Ecology, History of

Ecology descended from a tradition of natural history beginning in
antiquity. What has been called
protoecology
is seen in the writings of Carolus Linnaeus, a Swedish botanist, who, in
the eighteenth century, wrote of interactions of plants and animals, which
he called
The Economy of Nature.
In the early nineteenth century a German biogeographer, Alexander von
Humboldt, stimulated the study of the distribution of vegetation as
communities of plants and their environment that was pursued into the
twentieth century by such European botanists as Oscar Drude and Eugene
Warming. Edward Forbes, a British marine biologist, studied seashore
communities early in the nineteenth century and was among the first to use
quantitative methods for measuring water depth and counting individual
organisms.

Early Roots

The name
ecology
, however, was coined in 1866 by German biologist Ernst Haeckel, a
prominent proponent of Darwinism. In 1870 Haeckel wrote, "Ecology
is the study of all those complex interactions referred to by Darwin as
the conditions of the struggle for existence." (Darwin himself
figures prominently in protoecology.) Ecology emerged as a recognized
science in the 1890s and early 1900s as a mix of oceanography, its
freshwater counterpart limnology, and plant and animal ecology. It
departed from the late-nineteenth-century emphasis on laboratory studies
of physiology and genetics to return to the field emphasis of traditional
natural history. Premier British animal ecologist Charles Elton defined
ecology as scientific natural history.

In the United States, ecology flourished particularly in the Midwest. S.
A. Forbes of the Illinois Laboratory of Natural History initiated studies
of lakes and streams in the 1880s. In the 1890s Edward A. Birge pioneered
lake studies at the University of Wisconsin. Frederic Clements initiated
vegetation studies at the University of Nebraska and formulated ideas of
ecological communities in the 1890s that dominated American ecology for
fifty years. In the same decade Henry C. Cowles, from the University of
Chicago, studied the vegetation of the dunes of Lake Michigan.

Clements and Cowles, among the first to earn advanced degrees in ecology,
examined the changes of plant species populations, communities, and
environments over time, a process they called
succession
, adapting the term from poet-naturalist Henry D. Thoreau.
Clements's concept of succession, which dominated ecology until the
1950s, was of communities developing progressively to a relatively stable
state, or climax, that he said had properties of a superorganism. Ecology
became institutionalized in British and American ecological societies in
1913 and 1915, respectively.

Integration and Quantification

Charles Elton wrote the first book on animal ecology in 1927 and provided
organizing ideas that served to integrate population and community ecology
and remain as key concepts. These were:

Food chain or cycle (later called food web or trophic structure): the
sequence by which nutrients and energy passed from plants to herbivores
to predators then to various forms of decomposers and back to the
inorganic environment.

Niche: Each species had adaptations that fitted it to a particular
status in a community.

Pyramid of numbers: More small animals are required to support fewer
large organisms in a food chain because some nutrients and energy are
lost from the food chain.

The 1920s and 1930s also produced early developments in quantitative
ecology and mathematical theory. Ecological studies increasingly used
quantitative samples of populations and communities to assess the numbers
and kinds of organisms in a habitat and to measure the physical
environment. Theoretical, mathematical, population ecology was an attempt,
particularly by a physicist, Alfred Lotka, and a mathematical biologist,
Vito Volterra, to extend principles of physical chemistry into ecology in
the form of a differential equation, the logistic, that describes the
growth of a population over time.

Ecological theory flourished in the 1950s in the work of George Evelyn
Hutchinson and Robert MacArthur, who formulated a niche theory of animal
communities predicated on competition among species. Also in the 1950s,
the long-ignored, individualistic concept of community of Henry A.
Gleason, which held that organisms responded individualistically to the
physical environment and other organisms, was resurrected and became
widely accepted as alternative to the superorganism theory of Clements.
Ecologists became increasingly aware of the significance of historical and
chance events for developing ecological theory.

Ecosystems and Human Influences

British ecologist Sir Arthur Tansley recognized that it was not possible
to consider organisms apart from their physical environment, as ecologists
conventionally did, and in 1935 coined the term "ecosystem."
Ecosystems are integrated systems of living organisms (biotic) and
inorganic (abiotic) conditions. The ecosystem concept was integrated with
the trophic concept and succession in 1942 by a young American
limnologist, Raymond Lindeman. Ecosystem ecology focused on the movements
of matter and energy through the food web. Partly through the influence of
American ecologist Eugene Odum, ecosystem ecology became one of the
principal forces in ecology in the 1960s and 1970s and the basis of a new
theoretical ecology termed "systems ecology."

As ecology developed as a science it became evident that its concepts of
population, community, environment, and ecosystem must incorporate human
beings and their effects on Earth. This, too, had antecedents in
nineteenth-century natural history. In 1864 George Perkins Marsh argued
that

Ernst Haeckel, the German biologist who coined the term
"ecology."

human actions have profound, reciprocal, and commonly destructive effects
on the earth on which humanity depends. Early ecologists were acutely
aware of the implications of ecology for human environments and worked on
agricultural, fisheries, wildlife, disease, and conservation problems.
This insight became widely evident to the American public and politicians
with the recognition in the 1970s of the environmental crisis. In 1962
marine biologist Rachel Carson provided an early warning of the threat of
herbicides and pesticides to the environment, a warning for which she was
castigated by the chemical industry that produced them and the
agricultural industry that used them injudiciously.

Aldo Leopold, an American forester turned animal ecologist, published the
Sand County Almanac
in 1949 as a plea for an ecological view of the earth and of humanity.
Leopold wrote: "That land is a community is the basic concept of
ecology, but that land is to be loved and respected is an extension of
ethics." Leopold's ideas influenced conservationists and
philosophers, especially ethicists, and extended ecological ideas to a
concerned public.